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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 52 |
1 files changed, 52 insertions, 0 deletions
@@ -35285,6 +35285,58 @@ but produce lazy lists. -> (("defg" 5)) .brev +.coNP Functions @ keep-keys-if and @ separate-keys +.synb +.mets (keep-keys-if < predicate-fun < sequence <> [ key-fun ]) +.mets (separate-keys < predicate-fun < sequence <> [ key-fun ]) +.syne +.desc +The functions +.code keep-keys-if +and +.code separate-keys +are derived, respectively, from the functions +.code keep-if +and +.codn separate , +and have the same syntax and argument semantics. They differ in that +rather than accumulating the elements of the input +.codn sequence , +they accumulate the transformed values of those elements, as projected +through the +.metn key-fun . + +Thus when +.meta key-fun +is omitted, thus defaulting to +.codn identity , +or else explicitly specified as +.code identity +or equivalent function, the behavior of these functions is the +almost the same as that of +.code keep-if +and +.codn separate . +However, there may be a difference in whether the output shares structure with +.metn sequence . + +.TP* Example: + +.verb + ;; square the values 1 to 20, keeping the even squares + [keep-keys-if evenp (range 1 20) square] + -> (4 16 36 64 100 144 196 256 324 400) + + ;; square the values 1 to 20 separating into even and odd: + [separate-keys evenp (range 1 20) square] + -> ((4 16 36 64 100 144 196 256 324 400) + (1 9 25 49 81 121 169 225 289 361)) + + ;; contrast with keep-if: values are of input sequence + [keep-if evenp (range 1 20) square] + -> (2 4 6 8 10 12 14 16 18 20) +.brev + .coNP Functions @, countqual @ countql and @ countq .synb .mets (countq < object << iterable ) |